One of the most devastating and prolific weapons currently in use are rocket-propelled grenades which are launched, for instance, against jeeps or other vehicles from very short range in which the rocket-propelled grenade is a shoulder-launched weapon. These weapons are inexpensive and can cause tremendous damage, with no current effective countermeasure available. The incoming velocity of such rocket-propelled grenades is between 150 and 300 meters per second, and there is little time to react with any sort of a countermeasure. Particularly vulnerable are HUMMVs, which are used for patrols. However, other vehicles, including trucks and armored personnel carriers, are also vulnerable to such crude weaponry.
In order to countermeasure a rocket-propelled grenade, which must be done within a couple of milliseconds, it has been suggested to project 22 caliber rounds towards the rocket-propelled grenade to intercept the nose of the rocket-propelled grenade. This neutralizes the RPG by deactivating the fuse.
More particularly, it is known that rocket-propelled grenades explode on impact, with the impact being sensed at the nose of the rocket-propelled grenade. The impact trigger sends signals down the length of the rocket-propelled grenade to ignite its explosive charge. If the nose of the rocket-propelled grenade is somehow disabled, then the charge will not ignite and the RPG will strike the vehicle like a rock, with little damage.
The task therefore is to intercept the RPG in flight and to neutralize it before it can strike its intended target. From start to finish, from a launching, which may be as near as 50 feet away, to striking and detonating against a target, there are only milliseconds to sense the launch and countermeasure this type of threat.
One proposal had been for the projection of multi-spectral planes and to detect by the color of the reflected responses from a projectile going through the planes the exact position of the projectile, thereby to be able to launch an effective countermeasure against the incoming RPG. However, this type of system involves a large number of different detectors and transmitters and, more importantly, is a very complex and expensive system to build. It was therefore clear that a less expensive, more easily deployed system needed to be developed.
By way of further background, for instance with a jeep traveling down an urban street, the jeep is vulnerable to RPG attack, which takes place in two phases. The RPG, when shoulder-launched, travels at about 150 meters per second and then accelerates to close to 300 meters per second in the second phase. The dual speed process was an attempt to obtain an ordnance that could work from as much as 150 feet away from the target to as little as 50 feet. RPGs are not usually launched from a distance of more than 150 feet away because of their limited accuracy. Thus, even though the rocket-propelled grenade increases its velocity so as to make it a lethal weapon at larger range, its accuracy is so horrendous that those using RPGs prefer to get in close and preferably within 50 feet of the target.
A rocket-propelled grenade launched at 50 feet has a travel time of only a few milliseconds and it is therefore incumbent upon a countermeasure to quickly detect the presence of an RPG attack, locate the RPG and provide a countermeasure that involves damaging or incapacitating the nose of the RPG.